Jet-type reamer for use with drill pipe strings



July 8, 1969 J. MccLlNToN 3,454,119

i JET-TYPE BEAMER FOR USE WITH DRILL PIPE STRINGS Filed March 1e, 1967 22 25 BY Z United States Patent Olce 3,454,1 19 Patented July 8, 1969 U.S. Cl. 175-422 Y 4 Claims ABSTRACT OF THE DISCLOSURE A tubular sub insertible in a well drilling pipe string through which hydraulic pressure fluid is circulated, and provided with outwardly and downwardly directed jet nozzles for hydraulically removing mud cake from the wall of the well bore.

BACKGROUND OF THE INVENTION In the drilling of oil and gas wells by the conventional rotary method, a hydraulic fluid, commonly laden with clay and weighting material, is circulated through the well bore for the primary purpose of controlling the well against blowouts, to lubricate the bit and to wash cuttings from the well bore. The bore wall surface of the rock formations which are penetrated by the drill will usually be plastered with the solid matter carried bythe drilling fluid to form a cake or coating on the bore wall. Thereafter, when preparing to set and cement casing in the well bore, it is necessary first to remove as much as possible of the mud cake from the well wall in order to insure a good bond with the cement which is introduced to form a Huid-tight seal between the casing and the bore wall.

The removal of such mud cake is generally accomplished by means of mechanical devices, such as wire scratchers and the like, which are not always effective to sufficiently clean the bore wall. This is particularly true because the bore wall is rarely perfectly straight, and even under good conditions will have many cavities extending radially outwardly from the bore wall. These irregularities and cavities will be filled with mud cake, generally out to the nominal gauge of the bore wall, but by reason of their depths or thickness, cannot be satisfactorily removed by the conventional mechanical scratchers or the like, which ordinarily will have limited radial reach.

As a result of these deficiencies in conventional devices, many sections of the bore hole will remain coated with mud cake, with the further result that when the casing is run and the cement placed, a defective seal will result between the cement and the bore wall by reason of the inter-position of the unremoved mud cake. As a consequence, channels will develop in the cement body between the casing and the bore wall through which undesirable leakage of oil, gas and salt water will occur, which will be severely damaging to the well and may result in its destruction.

Accordingly, it is a primary object of the present invention to provide a tool for installation in a rotary drill pipe drilling string which employs the hydraulic pressure of the circulating drilling or washing fluid to hydraulically remove the mud cake from the bore wall, and which will be effective to remove such cake from cavities and other irregularities in the bore wall from which it would not ordinarily be effectively removed by conventional mechanical devices.

A further object is to provide a tubular sub having downwardly and outwardly directed jet nozzles through which the pressurized drilling or washing fluid may be propelled against the bore wall with suicient force to hydraulically ream the bore wall to a radial depth sufficient to substantially remove the mud cake.

SUMMARY OF THE INVENTION In accordance with the present invention, I have provided a tubular drill string member adapted to be inserted in a rotary drill string, preferably between the bit and the first drill collar. The sub is provided with a plurality of angularly spaced jet nozzles which are directed downwardly and outwardly of the body of the tool so as to project jets of fluid at the corresponding angle against the bore wall with suicient force to hydraulically wash the mud cake oit of the bore wall. The angle at which the jets are disposed will be selected to enable the hydraulic jets to reach out to a substantial distance radially outwardly of the nominal gauge of the bore wall in order to clean out cavities and other depressions or irregularities in the bore Wall.

Other and more specific objects and advantages of this invention will become more readily apparent from the following detailedv description when read in conjunction with the accompanying drawing which illustrates useful embodiments in accordance with this invention.

In the drawing, FIG. l is a longitudinal, partly sectional, view showing the jet reamer in accordance with this invention, installed in a drill pipe string in combination with one form of bit;

FIG. 2 is a view similar to FIG. l, illustrating the jet reamer in combination with another form of drill bit; and

FIG. 3 is a cross-sectional view taken along line 3 3 of FIG. 2.

Referring iirst to FIG. l, there is shown a well bore 10 passing through a plurality of rock formations 11, 12 and 13. The bore hole intersecting the latter formation is shown to be substantially enlarged radially to define a cavity 14 in which mud cake 15 has deposited and filled out the cavity to substantially the nominal gauge of the bore hole.

A drill pipe string 16 is shown inserted into the bore hole and carries a jet reamer in accordance with this invention, designated generally by the numeral 17, to the lower end of which is attached a conventional rotary drill bit B adapted to cut a bore to the nominal full gauge of the well.

The jet reamer comprises a tubular body 18, generally of the heavy walled type commonly employed in drill collars, and having an axial bore 19 which communicates with the bore of pipe string 16 and uid discharge passages 20 in the drill bit. The opposite ends of body 18 are provided with threaded boxes 18a-18a for connecting the tool at one end to pipe string 16 and at the other to bit B. Body 18 is provided with at least two angularly spaced passages 21 having jet nozzles 22 inserted in their outer ends. Passages 21 communicate at one end with bore 19 and at the other open to the exterior surface of body 18 through flat faces 23 which are formed by undercutting the periphery of the body at an angle which is substantially normal to the axis of passageway 21. 'Ihe surface of the body will be cut away from the bottoms of the notches to provide the inclined guide faces 24. Passages 21 and nozzles 22 are disposed at an acute angle to the longitudinal axis of the reamer and this angle is not less than 10 nor more than 30 to assure that the iiuid jets leaving nozzles 22 will strike the bore wall sharply at such an angle as to effectively wash the relatively soft mud cake olf of the relatively harder earth formations. The angle will also direct the jets radially outwardly to a suiicient extent to effectively reach out into cavities, such as cavities 14, and wash the mud cake out of these cavities, as illustrated in FIG. l. Guide faces 24 will also preferably be inclined at the same angle as that of the nozzles.

Nozzles 22 are constructed of hard abrasion-resisting material, such as tungsten carbide, and have reduced diameter orifices 25 such that the pressure of the fluid being pumped through the drilling string will provide jets of high pressure and high velocity, which will be directed against the bore wall with suicient force and at an angle to .accomplish the teaming action desired.

FIG. 1 illustrates diagrammatically an operation, commonly referred to as a clean-up trip, which is usually conducted after the bore hole has been drilled to a desired depth, and which must then be prepared for setting the casing. This then involves running the string of drill pipe carrying the bit and the reaming tool back into the well bore and running it through the well bore while circulating hydraulic fluid to enable the removal of the mud cake from the bore wall preparatory to running the casing.

The jet reaming tool, in accordance with this invention, may be installed initially in the rotary drilling string employed to drill the original bore hole and will serve to keep excessive deposits of mud cake off of the bore wall as the drilling proceeds, so that in some cases a clean-up trip may not be necessary and where necessary, will involve a minimum amount of effort in effectively cleaning the bore wall.

FIG. 2 illustrates a modilication in which the jet reamer 17 is installed in a drill pipe string 16a equipped with a different form of bit B1 than that shown in FIG. l, and which also carries a plurality of radial stabilizers or centralizers 26 commonly employed on rotary drill strings. Functionally, the jet reamer in the system illustrated in FIG. 2 will operate in the same manner as previously described for removing excessive mud cake a from -the bore wall 10a.

As one example of a jet reamer in accordance with this invention, body 18 will be constructed of drill collar stock, having a length of about 30 feet and an external diameter of 8 inches. Three of the jet passages21 carrying the nozzles 22 will be provided on 120 spacing and will be inclined at an angle of 15 to the longitudinal axis of the tool. The diameter of passages 21 will be 11/8 and orifices 25 in the nozzles will be about inch in diameter.

It will ybe understood that modifications may be made in the details of the illustrative embodiments within the scope of the appended claims but without departing from the spirit of this invention.

What I claim and desire to secure by Letters Patent is:

1. A jet type reamer for drill pipe strings, comprising, a tubular body having an axial bore, means on the opposite ends of the body for connecting it into a pipe string, a plurality of angularly spaced passages communicating said bore with the exterior of the body, jet nozzles in the outer ends of said passages, said nozzles being inclined downwardly and outwardly at an angle from 10 to 30, the exterior surface of said -body being undercut to provide a at face for the terminus of each jet nozzle, and to provide an inclined guide surface extending from the inner end of said face to the exterior surface of the body.

2. A jet-type reamer according to claim 1, wherein said angle is 15.

3. A jet-type reamer according to claim 1 having at least two of said jet nozzles.

4. In a well drilling system employing a drill pipe string carrying a drill bit through which hydraulic pressure fluid is circulated through a well bore during operations therein, a jet-type reamer for removing mud cake and the like from the wall of the well bore, comprising,

(a) a tubular body mounted in said pipe string above and closely adjacent the bit and having an axial bore in communication with that of the pipe string,

(b) a plurality of .angularly spaced passages through the wall of said body communicating said axial bore with the exterior of said body,

(c) jet nozzles mounted in the outer ends of said passages to have their discharge ends terminate inwardly of the exterior surface of said body,

(c1) said exterior surface of said body being undercut to provide a lat face for the terminus of each jet nozzle, and to provide an inclined jet guide surface extending from the inner end of said face to the exterior surface of the body,

(d) said nozzles being downwardly and outwardly inclined relative to the longitudinal axis of the body at an angle Within the range of 10 to 30, whereby to direct said hydraulic pressure iluid downwardly at said angle against the wall of said well bore.

References Cited UNITED STATES PATENTS 1,994,884 3/1935 Chew 175--422 X 2,312,018 2/1943 Beckman 166--44 X 2,518,591 8/1950 Aston 175-422 X 2,771,141 11/1956 Lewis 166-222 2,785,875 3/1957 Hayes 175-422 X 3,116,800 1/1964 Kammerer 166-222 X 3,123,159 3/1964 Buck 175-67 3,077,936 2/1963 Arutunolf 175-404 X NILE C. BYERS, IR., Primary Examiner. 

